Fuel injection system for externally ignited internal combustion engines

ABSTRACT

IN A FUEL INJECTION SYSTEM, THE FUEL ADMITTED TO THE FUEL INJECTION VALVE IS METERED BY A PLUNGER ANGULARLY DISPLACEABLE BY A THROTTLE MEMBER RESPONSIVE TO THE AIR PRESSURE IN THE SUCTION TUBE. PRIOR TO THE INJECTION OF FUEL BY THE INJECTION VALVE INTO THE SUCTION TUBE, THE FUEL IS PREMIXED IN SAID INJECTION VALVE BY AIR TAKEN FROM THE SUCTION TUBE DOWNSTREAM OF SAID THROTTLE MEMBER AND UPSTREAM OF AN ARBITRARILY OPERABLE BUTTERFLY VALVE.

Sept. 21, 1971 ECKERT 3,606,872

- FUEL INJECTION SYSTEM FOR EXTERNALLY IGNITED INTERNAL COMBUSTION ENGINES Filed July 9, 1970 IN VEN TOR.

BY I

United States Patent 3,606,872 FUEL INJECTION SYSTEM FOR EXTERNALLY IGNITED INTERNAL COMBUSTION ENGINES Konrad Eckert, Stuttgart-Bad Cannstatt, Germany, assignor to Robert Bosch GmbH, Stuttgart, Germany Filed July 9, 1970, Ser. No. 53,344 Claims priority, application Germany, July 9, 1969, P 19 34 705.8 Int. Cl. F02b 33/00; F02m 39/00 US. Cl. 123119R 5 Claims ABSTRACT OF THE DISCLOSURE In a fuel injection system, the fuel admitted to the fuel injection valve is metered by a plunger angularly displaceable by a throttle member responsive to the air pressure in the suction tube. Prior to the injection of fuel by the injection valve into the suction tube, the fuel is premixed in said injection valve by air taken from the suction tube downstream of said throttle member and upstream of an arbitrarily operable butterfly valve.

BACKGROUND OF THE INVENTION This invention relates to a fuel injection system for externally ignited internal combustion engines and is of the type wherein the fuel is injected continuously into the suction tube in which there are disposed in series an arbitrarily operable butterfly valve and a throttle member. The latter, actuated by the upstream and downstream pressure prevailing in the suction tube, controls a metering valve disposed in the fuel conduit and operating with a constant pressure drop. Said system is further of the type that includes at least one fuel injection nozzle in which the fuel is premixed with intake air from the suction tube.

In a known fuel injection system of the aforenoted type (such as disclosed in German Patent No. 1,243,917), the throttle member displaces the throttle needle of the fuel metering valve, the contour of which is designed in such a manner that for each flow rate of air there corresponds a predetermined flow rate of fuel. For this purpose, the momentary flow passage section of the throttle member may be made proportionate to the momentary flow passage section of the fuel metering valve.

The shaping of the throttle needle contour is relatively expensive. Further, in particular, the adjustment of the throttle needle and throttle bore of the fuel metering valve with respect to the position of the throttle member,

as well as the alteration of the fuel-air mixture duringoperation of a hot engine or for providing a rich mixture of the starting fuel quantities, are restricted to relatively narrow limits.

In the aforenoted known fuel injection system, the air with which the fuel is to be premixed, may be taken from the suction tube upstream of the throttle members. Thus, this air quantity, which, too, takes part in the combustion, is not sensed by the throttle member and, accordingly, cannot be accounted for in the metering of the fuel, or, the air may be taken from the suction tube downstream of the throttle members. In such a case an air pump is necessary since the pressure or the weight of the air in the suction tube portion downstream of the throttle members is approximately the same as at the location of injection.

Also, in fuel injection nozzles of the aforenoted ty:pe which, in order to obtain a favorable metering of fuel to the individual engine cylinders, are disposed in the vicinity of the suction valves of the engine-it cannot be avoided that during pushing operation, in which the butterfly valve is closed, fuel is drawn from the fuel line by means of the strong vacuum in the suction tube. This fuel is then admitted to the engine cylinders. The fuel 3,606,872 Patented Sept. 21, 1971 mixture obtained in such a manner is in most cases not combustible which leads to poisonous exhausts. Or, if the mixture is combustible, a jerky run of the engine results.

OBJECT AND SUMMARY OF THE INVENTION It is an object of the invention to provide an improved fuel injection system of the aforenoted type in which the disadvantages set forth above are eliminated.

It is a further object of the invention to provide an improved fuel injection system of the aforenoted type in which the air to be premixed with fuel has, at the location of injection, without the aid of an air pump, a pressure which is larger than that prevailing in the suction tube.

Briefly stated, the aforenoted objectives are achieved, according to the invention, by the combination of the following, partially known features:

(a) The fuel metering valve includes a control plunger which has an oblique control edge and which is turnable by the throttle member to thus determine a free flow passage section for the fuel dependent upon its angular position; said control plunger is also axially displaceable for closing completely said flow passage section;

(b) At the fuel injection valve the fuel is first injected by means of a liquid fuel injection nOZZle through an intermediate air chamber and thereafter forwarded by means of an intermediate nozzle aligned with the liquid nozzle, While air is admitted to the intermediate air chamber (as discussed, for example, in U.S. Pat. No. 3,330,541);

(c) The air admitted to the fuel injection valve is taken from the suction tube between the butterfly valve and the throttle member;

(d) In the fuel injection valve there is disposed a closing member which is adapted to obturate the liquid nozzle and which is open during normal operation; said closing member is operable against a return force by a control liquid admitted through a control conduit; and

(e) When the flow passage section of the fuel metering valve is closed, the control plunger establishes hydraulic communication between the fuel line and the normally depressurized control conduit of the fuel injection valve.

The invention will be better understood as well as further objects and advantages will become more apparent from the ensuring detailed specification of a preferred, although exemplary, embodiment of the invention taken in conjunction with the sole drawing showing the embodiment in section.

DESCRIPTION OF THE PREFERRED EMBODIMENT In a suction tube 1, intake air flows past a throttle member 2 and an arbitrarily operable butterfly valve 3 to a cylinder or cylinders (not shown) of an internal combustion engine (also not shown).

A cylindrical throttle member 2 extends transversely to the direction of air flow into the suction tube 1 through an orifice 4 provided in the tube wall. It is to be understood that the said cylinder' throttle member may be replaced by a pivoting gate or a baflle plate displaceable in the direction of air fiow. The displacement of the throttle member 2 in the suction tube 1 is approximately a linear function of the air quantity passing through the suction tube 1. The pressure prevailing between the throttle member 2 and the butterfly valve 3 remains approximately constant assuming a constant pressure upstream of the throttle member 2.

The throttle member 2 is integral with a piston 5, the diameter of which is greater than that of the throttle member 2. The piston S is received with a snug fit by and is displaceable in a cylinder 6. The piston 5 is pulled radially outwardly of the suction tube 1 against the re turn force of a spring 9 by means of the vacuum prevailing in the suction tube portion 1a between the throttle member 2 and the butterfly valve 3. The vacuum conditions prevailing in the suction tube portion 1a are communicated to cylinder 6 through a channel 8. The annular space defined in the cylinder 6 by the throttle member 2 and the adjacent radial annular face of the piston 5 communicates by means of a channel 7 either with the atmosphere or, as shown, with the air inlet 1d of the suction tube 1. It is to be understood that instead of piston 5,the throttle member 2 may be associated with a membrane or any other equivalent actuating means. The slope of the linear function between the displacement of the throttle member 2 and the air quantity depends upon the characteristic of the spring 9, as well as upon the frictional losses between the contacting faces of the sliding members. To the throttle member 2 there is affixed, for simultaneous displacement therewith, a toothed rack 10, the teeth of which mesh with a pinion 12 which is arranged circumferentially about a turnable control plung 11.The latter forms the movable part of the fuel metering valve. It is thus seen that to each axial position of the throttle member 2 there corresponds a determined angular position of the control plunger 11.

In the lateral face of the control plunger 11 there is provided an annular groove 14, one axial boundary of which is formed as an oblique control edge 14' for controlling the flow passage section 22 of a preferably rectangular longitudinal groove 15. A fuel pump 16, which is driven by an electric motor 17, draws fuel from a tank 18 and delivers it through a conduit 19 into the annular groove 14. From the conduit 19 there extends, immediately downstream of pump 16, a return conduit 20 in which there is arranged a pressure limiting valve 21.

From the annular groove 14 the fuel flows through the metering flow passage section 22 ,into the groove 15 and therefrom into a bore 23 which leads to a membraneoperated plunger valve 24. The latter, which maintains the pressure drop at the metering throttle 22 at a constant value, includes an annular chamber 25 into which merges the bore 23 and a control plunger 26 which is actuated by a membrane 27. The lateral face of the control plunger 26 is provided with an annular groove 28 which communicates with a conduit 29 leading to the fuel injection valve or valves 34 (only one shown). One axial boundary of the groove 28 controls the flow passage section defined jointly by the groove 28 and the chamber 25.

The spaces-at either side of the membrane 27 are connected hydraulically by means of conduits with locations upstream of and downstream of the metering throttle 22. Thus, the space 27, in which hydraulic pressure tends to displace the valve 24 in the closing direction upon increasing fuel pressure upstream of throttle 22, is connected by means of a conduit 30 with the conduit 19. The space 27" on the other hand, in which hydraulic pressure tends to displace the valve 24 in the opening direction, is connected by a channel 31 with the conduit 23. If the pressure changes upstream of the metering throttle 22 or, downstream thereof, in the conduit 29 and, as a result, the pressure drop at the metering throttle 22 is changed, the control plunger 26 is, by means of the membrane 27, displaced against the force of a return spring 33. Such displacement is in progress until, by virtue of the throttle effect of the slide valve 24, the previous pressure drop at the metering throttle 22 is re-established. The pressure drop is determined mainly by the stiffness of the membrane 27 and the force of the spring 33. The pressure drop is thus constant and independent of the fuel quantities flowing through the fuel conduit 29.

The control plunger 11 is axially displaceable against the force of a return spring 35 which presses it against a fixedly but adjustably held abutment 36. For changing the fuel-air mixture, the abutment 36 is, arbitrarily or by means of a suitable device, rotatable whereby the ratio of the flow passage section of the throttle member 2 to that of the fuel metering throttle 22 is varied. Such setting 4 is effected for the pre-adjustment of the flow passage section ratio and also, during starting or hot run of the engine of a richer air-fuel mixture is required.

The terminus of the control plunger 11 remote from the abutment 36 ,is surrounded by an electromagnet 37. When the latter is energized, the control plunger 11 is displaced axially against the force of a return spring 35. Upon such an occurrence, hydraulic communication is interrupted between the annular groove 14 and the groove 15 so that the flow of fuel into the fuel injection valve or valves 34 is cut off. This is particularly required during pushing operation to avoid an excessive ratio of poisonous matter in the exhaust and to prevent a jerky operation of the engine.

Each fuel injection valve 34 is provided with a closing member 38 which, during the pushing operation, is, by hydraulic pressure, displaced against the force of a return spring 39 closing thereby the nozzle opening 40 of a liquid nozzle. In this manner it is prevented that during the pushing operation, fuel is drawn from the fuel conduit 29. Such occurrence would again result in the aforenoted disadvantages. For a hydraulic control of the closing member 38 there is provided a conduit 41 which communicates with an annular groove 42 disposed on the lateral face of the control plunger 11. The annular groove 42, in turn, communicates through a channel 43 with a chamber receiving the spring 35. In channel 43 there is disposed a pressure maintaining valve 44. The latter has solely the purpose to prevent the fuel present in the conduits and channels 41, 42 and 43 from escaping. It does not prevent, however, the closure member 38 of the fuel injection valve 34 from being displaced by the spring 39 into its initial position as shown when the control plunger 11 is in a position as illustrated in the drawing.

As soon as the control plunger 11 is displaced by the electromagnet 37 and thereby the fuel admission to the fuel injection valve or valves 34 is interrupted, the annular groove 14 of the control plunger 11 is connected with the conduit 41, whereby the fuel delivered by the pump 16 exerts a pressure on the closing member 38 with a force determined by the pressure control valve 21. As a result, the closing member 38 is displaced against the force of the return spring 39 and closes the injection nozzle 40. It is thus seen that simultaneously with the interruption of the fuel admission, the fuel injection nozzle 40 is also closed.

From the conduit 29 the fuel is admitted to a vortex chamber 50 of the fuel injection valve through a channel 49 disposed in the nozzle body and through bores 49' disposed tangentially wilh respect to said chamber. From the latter, the fuel is forwarded, in a turbulent condition, into an intermediate air chamber 51 by means of a liquid nozzle 40. Thereafter, the fuel is injected, by means of an intermediate nozzle 52, into the suction tube 1 of the internal combustion engine.

Into the intermediate air chamber 51 there merge air channels 53 (only one shown) provided in the nozzle body. The air channels 53 are connected through a conduit 54- with the suction tube portion 1a extending between the throttle member 2 and the butterfly valve 3. In suction tube portion 1a there prevails a pressure which is relatively larger than that prevailing in the suction tube portion into which the fuel injection nozzle 34 merges. Consequently, the air enters from the conduit 54 and channels 53 under pressure into the intermediate air chamber 51. Such condition is advantageous for a good preparation (premix) of the fuel by means of air. Further, the air to be premixed with the fuel is taken from a location in the suction tube which lies downstream of the throttle member, so that this air quantity, too, is taken into account when the fuel is metered.

In the conduits 29, 41 and 54 there are disposed distributors 56, 57 and 58, respectively, which have as many branch conduits as there are injection valves 34 associated with the fuel injection system.

That which is claimed is:

1. In a fuel injection system for externally ignited internal combustion engines, said system being of the known type that includes (A) a suction tube through which intake air is drawn, (B) an arbitrarily operable butterfly valve disposed in said suction tube, (C) a throttle member disposed in said suction tube and actuated by the air pressure prevailing in said suction tube upstream and downstream of said throttle member, (D) a fuel injection nozzle in which fuel is premixed with air taken from said suction tube, '(E) fuel conduit means to deliver fuel to said fuel injection nozzle, and (F) a fuel metering valve operating with a constant pressure drop in said fuel conduit means and actuated by said throttle member for controlling the flow of fuel to said fuel injection nozzle, the improvement comprising in combination,

(A) a control plunger forming part of said fuel metering valve, said plunger including an oblique control edge determining a flow passage section for said fuel in said fuel conduit means,

(B) means connecting said throttle member with said control plunger for turning the latter in response to the displacement of said throttle member to vary said flow passage section,

(C) means for axially displacing said control plunger for entirely closing said flow passage section to cut off fuel supply to said fuel injection nozzle,

(D) a liquid nozzle forming part of said fuel injection nozzle,

(B) an intermediate air chamber forming part of said fuel injection nozzle and arranged downstream of said liquid nozzle in communication therewith,

(F) an intermediate nozzle forming part of said fuel injection nozzle and arranged downstream of said intermediate air chamber aligned with said liquid nozzle,

(G) means for introducing into said intermediate air chamber air taken from said suction tube between said butterfly valve and said throttle member,

(H) a closing member movable in said fuel injection nozzle for cutting off the injection of fuel when moved in a closed position,

(I) a hydraulic control conduit leading from said control plunger to said closing member, and

(J means for establishing communication between said fuel conduit means and said hydraulic conduit for moving said closing member into said closed position when said flow passage section is closed.

2. An improvement as defined in claim 1, including electromagnetic means for axially displacing said control plunger.

3. An improvement as defined in claim 1, including a pump for delivering fuel under constant pressure to said fuel metering valve.

4. An improvement as defined in claim 3, including electric motor means for driving said pump.

5. An improvement as defined in claim 1, including (A) a vortex chamber forming part of said fuel injection nozzle and disposed upstream of said liquid nozzle, and

(B) at least one fuel supply channel merging tangentially into said vortex chamber.

References Cited UNITED STATES PATENTS 2,876,758 3/1959 Armstrong 123119R 3,320,893 5/1967 Koster et al. 4l7293 2,253,455 8/1941 Eideneier 123-1402 2,800,121 7/1957 Fletcher 123-119R 3,517,688 6/1970 Scholle 25163.6 3,198,498 8/1965 Mennesson 123119R 2,511,213 6/1950 Leslie 123139.17 3,330,541 7/1967 Jackson 261-231 MARK M. NEWMAN, Primary Examiner C. R. FLINT, Assistant Examiner US. Cl. X.R. 123-140MC 

